In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
In the following, reference will be made to UMTS and to particular standards. However it should be understood that the present disclosure is not intended to be limited to any particular mobile telecommunications system or standard.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which in UMTS may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Cell selection, sometimes referred to as cell search, for a UE is described in the 3GPP TS 25.304 specification, v 8.1.0, “User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode” which is incorporated herein by reference and referred to herein as the 25.304 specification. Section 5.2.3 and in particular section 5.2.3.1.1 of the 25.304 specification describes the cell selection process.